Pneumatic interconnection board

ABSTRACT

A laminated board made of two sheets of aluminum and providing closed conduits for transmitting fluid pressures between pneumatic components secured to the board. One sheet is pressformed to provide groovelike channels; the other sheet is sealed to the first sheet and is formed with connection holes leading to the passages defined by the press-formed channels. The two sheets are bonded together by an epoxy preform having a configuration matching that of the circuit board and sealing the passages from leakage.

United States Patent lloel L. Bowditch Foxboro, Mass.

Oct. 6, 1969 Jan. 4, 1972 The Foxboro Company Foxboro, Mas.

Continuation-impart 01 application Ser. No. 772,601, Nov. 1, 1968, nowabandoned. This application Oct. 6, 1969, Ser. No. 864,108

lnventor Appl. No. Filed Patented Assignee PNEUMATIC INTERCONNECTIONBOARD 34 Claims, 10 Drawing Figs.

US. Cl 137/271, 29/157.3,113/116,137/608,138/111 Int. (1 Fl5c 5/00, F15c1/06, F15c 3/04 Field of Search 137/608,81.5,271;138/115,116,177,l78,11l;29/l57.3 D; 113/116 [56] ReferencesCited UNITED STATES PATENTS 3,298,460 1/ 1967 Porter et a1. 184/73,384,115 5/1968 Datzan et al.... 137/608 3,407,833 10/ 1 968Brandenberg..... 137/271 3,407,846 10/1968 Brandenberg 137/608 2,882,5884/1959 Rieppel et al. 29/D1Gv 32 2,920,463 1/ 1960 Gould 29/DIG. 322,944,328 7/1960 Adams 29/DIG. 32 3,018,543 l/l962 Beck 113/118 XPrimary Examiner-M Cary Nelson Assistant Examiner-Robert J. MillerAttamey--Bryan, Parmelee, Johnson & Bollinger ABSTRACT: A laminatedboard made of two sheets of aluminum and providing closed conduits fortransmitting fluid pressures between pneumatic components secured to theboard. One sheet is press-fonned to provide groovelike channels; theother sheet is sealed to the first sheet and is formed with connectionholes leading to the passages defined by the press-formed channels. Thetwo sheets are bonded together by an epoxy preform having aconfiguration matching that of the circuit board and sealing thepassages from leakage.

mm.- 4812 I 3.631.881 SHEET 2 [1F 4 LMMILL'LJ PNEUMATIC INTERCONNECTIONBOARD This application is a continuation-in-part of pending applicationSer. No. 772,601, filed on Nov. 1, 1968, and now abandoned.

This invention relates to industrial process instrument systems of thepneumatic type. More particularly, this invention relates toimprovements in pneumatically interconnecting the components of suchsystems.

Pneumatic instruments have been used for many decades with industrialprocesses to measure and/or control process conditions such astemperature or flow rate. These instruments generally perform a numberof different but interrelated functions to effect some desired endresult. The functions performed may for example include some combinationof the following:

1 producing a motion corresponding to a sensed pressure,

2. developing a pneumatic signal in response to the degree of unbalancebetween two opposed forces,

3. varying a rebalance force to maintain the forces on an element inbalance,

4. altering a pneumatic pressure signal as a function of itsrate-of-change or time-integral,

5. amplifying a pneumatic signal, and so forth. A typical instrumentsuch as a process controller ordinarily contains a number of separatecomponents for accomplishing corresponding functions.

The individual components of a pneumatic instrument mustbeinterconnected in such a way as to transmit fluid pressure signalstherebetween to satisfy the system requirements, and connections also ofcourse must be provided to supply air under pressure to such componentsas require it. Generally these interconnections have in the past been inthe form of sealed piping or tubing adapted to conduct fluid underpressure to and from the separate components. Although such arrangementshave been functionally effective, they have not been well adapted toeconomical manufacture, particularly for the more recent highly complexinstruments requiring multiple interconnections. The use of conventionaltubing and piping also does not lend itself well to the compactinstrumentation so essential to the proper instrumenting of modernprocesses involving large numbers of variables all controlled byinstruments clustered at a central station.

In a preferred embodiment of the present invention, to be describedbelow in detail, there is provided a new technique for producing thefluid interconnections required in pneumatic instruments. This newtechnique comprises the development and use of what might be termed apneumatic circuit board which is manufactured as an integral unit andprovides all (or substantially all) of the interconnections needed forthe multiple, components of a corresponding instrument. This circuitboard also may advantageously serve to physically support at least someof the components of the instrument.

' The circuit board with its components may readily be secured in aninstrument by elongate guide rails.

The circuit board of the disclosed embodiment basically comprises twoaluminum plates which are bonded together face-to-face by epoxy resincement provided as a preform of impregnated fiberglass. One plate(called the mounting plate") is planarand rigid but formed with a set ofconnection holes. The other plate (called the circuit plate) ispressureforrned with ridgelike elements to define sealed fluid flowpassages extending between the connection holes. Such a circuit boardcan readily be manufactured in quantity and assembled with itsassociated components by conventional procedures at modest expense, andwill provide long periods of trouble-free operation.

Accordingly, it is an object of this invention to provide improvedpneumatic instrumentation for use with industrial processes. Anotherobject of this invention is to provide new techniques forinterconnecting the individual components of a complex pneumaticinstrument. The invention also comprises structural embodiments andmethods for making such structures. Other specific objects, advantagesand aspects of the invention will in part be pointed out in, and in partapparent from, the following description considered together with theaccompanying drawings in which:

FIG. 1 is a perspective of an instrument including a circuit board inaccordance with the present invention;

FIG. 2 is a perspective of a blanked circuit plate prior to shaping;

FIG. 3 shows a press in which the circuit plate of FIG. 2 is shaped bypressure-forming;

FIG. 4 is a detail section along line 4-4 of FIG. 3, when the press isclosed;

FIG. 5 is an exploded perspective of the principal elements of thecircuit board;

FIG. 6 shows an oven for curing the bonding cement of the circuit board;

FIG. 7 is an enlarged perspective of a part of the pressformed circuitplate;

FIG. 8 shows a circuit board with typical components mounted thereon;

FIG. 9 is a vertical section through one of the components, lookingtowards the circuit board; and

FIG. 10 is a section along line 10l0 of FIG. 1, to show the connectionsbetween the circuit board and the supply and signal conduits.

Referring first to FIG. 1, there is shown in perspective a pneumaticindicating controller 10 of the small case type adapted for high-densitypanel mounting, such as in a central control station. Such controllersare arranged to receive pneumatic pressure signals, e.g. in the range of3-l5 p.s.i., and to produce corresponding pneumatic control signals fortransmission to process valves or other associated units of the system.The instrument may include a front panel indicator 12 to display one ormore signal levels for the control station operating personnel.

The controller 10 includes a vertically mounted circuit board, generallyindicated at 14, which is supported at its upper and lower edges byguide rails 16 and 18. This circuit board is a laminated sandwichstructure consisting of a rigid aluminum mounting plate 20 (extendingthe full length of the controller) and a circuit plate 22 bonded to themounting plate by a layer or film of cement 24. Secured to the oppositeside of the mounting plate are a number of separate pneumaticcomponents, two of which (26, 28) can be seen through the centralopening 30 formed in the particular circuit board disclosed herein toprovide mechanical clearance for certain operating elements, not shownherein.

FIG. 2 shows the circuit plate 22 in flat condition, blanked inpredetermined geometrical configuration and pierced with a number ofholes as at 32. (Note: These holes 32 are for mounting screws andalignment rivets, and do not play any part in the pneumatic passages tobe disclosed.) This plate 22 is made of dead soft aluminum, e.g. typell00D having a uniform thickness of about 0.0l5-0.0l6 inch. Afterpiercing, the plate may be smoothed by the application of pressure froma set of flat dies, to eliminate burrs and collars.

The blanked-out flat plate 22 is placed in a forming press illustratedat 34 in FIG. 3, and which includes an upper reciprocating head 36carrying a precision female die 38, and a lower support 40 having aresilient male die 42 such as a pad of polyurethane. The female die isformed with a complex pattern of groovelike recesses so that, when thepress is closed (FIG. 4), the resilient male die acts somewhat in thenature of a liquid to force the thin aluminum material up into the dierecesses. Thus the aluminum plate is pressure-formed with a series ofridges 46 identical in configuration to the recesses of the female .die.These ridges define on the opposite sides thereof corresponding lateralgrooves 48 extending laterally along the face of the plate (see alsoFIG. 7).

In press-forming the aluminum plate 22 with such grooves, the aluminummetal is stretched somewhat in the localized regions adjacent thegrooves. This stretching of the aluminum can aid in producing thedesired flat surfaces between the grooves by a process which can betermed stretch-leveling," where parts of the original planar sheetportions between the grooves are stretched laterally into the formedpassages, causing the remaining intergroove portions to be flattened asthe stretching proceeds. That is, such stretching, under pressure fromthe planar portions of the dies, tends to level the aluminum material,as by removing any crinkles or other surface irregularities. To producethe best results, it is desirable to use a female die presentingrelatively large radii of curvature in the groove surfaces.

FIG. 5 shows the pressure-shaped circuit plate 22 together with themounting plate 20 and a sheet 50 of bonding material used to securethe'two plates together.

The mounting plate is relatively thicker than the circuit plate, andprovides rigidity for the laminated structure. This mounting plate canbe formed by conventional stamping procedures, and is made with a numberof holes such as illus: trated at 52. Some of these holes are forbolting components in place. Other holes are formed in a pattern adaptedto provide communication with grooves 48 when the plates are bondedtogether.

Prior to assembling the elements of FIG. 5, the aluminum surfaces to bebonded preferably are treated, chemically and/or mechanically, toprovide a good adhesion in the subsequent bonding step of the process.The treatment particularly should remove any silicones used duringmanufacture of the aluminum. The aluminum surfaces may be cleaned byimmersion in a solution of sulfuric acid and sodium dichromate, at 155F., for minutes. Thereafter, the surfaces are rinsed with circulatingcold water, followed by a hot water rinse, and hot air drying. Thealuminum surfaces may also be treated with commercially availablechromate conversion coatings, such as that supplied by The DiverseyCorporation, Chicago, Ill., providing a good adherent base, and reducingoxidation problems.

The sheet 50 of bonding material comprises a thin (0.003 inch)fiberglass mat, or matrix, impregnated with B-stage epoxy. Thisimpregnation includes both the epoxy resii't and its catalyst, in solidform. The use of a solid bonding material is superior to liquid cement,in its application to the present invention, because it insures uniformthickness of the bonding layer and avoids problems with cement flowingout from between the aluminum plates. The impregnated fiberglass mat maybe cut out from a large sheet, as by means of a production blanking die,to provide the cement material as a preform. Satisfactory results havebeen achieved by dies having a clearance of 0.002 inch which stroke pastthe die closing point by only 0.010 inch.

Special care preferably should be exercised to assure that moisture isnot absorbed into the epoxy preform, e.g., during storage awaiting use.Thus the prepared preforms should be stored with dessicants. Whenassembling the circuit boards manually, cotton gloves may be worn toavoid introducing moisture. The three elements preferably aremechanically aligned during assembly, as with the aid of alignmentrivets inserted through a selected set of the holes formed in the twoplates'20 and 22 and in the preform 50. This preform also is 'cut withadditional holes aligned with the pneumaticcomm-unication holes in thecircuit board.

The assembled laminate is thereafter placed in an oven 60, illustratedschematically in FIG. 6. This oven includes heater means 62 to heat thepreform to its curing temperature, e.g. 340 F. Desirably, the rate oftemperature rise should be 4 to 8 per minute, and the curing temperatureshould be maintained for about 10 minutes. I

Superior results are achieved by applying uniformpressure to the entireepoxy preform during the curing process. Advantageously, this isaccomplished by means of a flexible diaphragm 64 which forms the top ofa sealed chamber 66 within which the circuit board structure 14 isplaced. During the curing operation, this chamber is evacuated so thatatmospheric pressure forces the circuit plate 22 downwardly, withuniform pressure, against the epoxy preform 50. Experience has shownthat a pressure of almost 10 p.s.i.

produces good results. The alignment rivets of the assembly can serve asstandoffs to hold the mounting plate 20 a small distance above thesupport shelf 68, and insure rapid and uniform evacuation beneath allregions of the mounting plate.

FIG. 8 illustrates the manner in which a variety of components aresecured to the outer surface of the mounting plate 20 (the term outer"is used with reference to the circuit board structure 14, not theinstrument per se). These components may, for example, include a set ofbellows 26 each of which communicates through a corresponding hole inplate 20 to a respective groove 48 in the circuit plate 22.

FIG. 9 shows the interior of another type of pneumatic component 70which is especially adapted for use with the new circuit board structurebecause it provides relatively complex yet precise functions in anextremely small package. This component incorporates a pivotal diaphragmelement 72 sealed with a rubber sheet 74 to define two sets of opposedpressure chambers 76, 78 and 80, 82 at opposite sides of the pivot line.These chambers connect through respective passages 76a, 78a; 80a, 82a toholes 84, 86; 88, 90 in the side of the component which is held pressedagainst the outer surface of the mounting plate 20. These holes arealigned with corresponding holes in the mounting plate to makeconnection to respective grooves 48 in the circuit plate. Thisconnection may be sealed by conventional gasketing, such as by O-rings92 between the component 70 and the mounting plate.

FIG. 10 illustrates the manner in which the circuit board structure maybe connected to the supply and signal conduits leading to other parts ofthe system. As can be seen, the end wall of the circuit board is boltedfinnly against a chassis member 96 formed with conduits 98 the openingsof which are aligned with corresponding holes in the mounting plate.Again, suitable gasketing 100 is provided to effect a proper sealing ofthe connections.

I claim:

1. For use with pneumatic instruments and the like, a rigid circuitboard structure for establishing pneumatic interconnections betweencomponents of the instrument, said circuit board structure comprising:

a first plate of relatively thin, forrnable material of at leastapproximately uniform thickness, said first plate being pressed out inselected regions to form a predetermined complex pattern of ridgelikeelements defining on the opposite sides thereof grooves extendinglaterally along the plate;

a second plate abutting said first plate in face-to-face relationshipand cooperating with said grooves to establish closed passageways forthe transmission of gaseous fluid under pressure; and

means bonding said two plates together to produce a composite laminatedsandwich providing pressuretight sealing of said passageways, one ofsaid plates being formed with openings communicating through said oneplate at least to certain of said passageways to provide for connectionto a component of the instrument.

2. A structure as claimed in claim 1, wherein said first plate isstretch-formed with said ridges and said second plate is formed with,said openings communicating with said passageways.

3. A structure as claimed in claim 2, including at least one pneumaticcomponent secured to said second plate and positioned over at least oneof said openings to establish communi-. cation therewith.

4. A structure as claimed in claim 3, wherein said first and secondplates are made of metal; said second plate being thicker than saidfirst plate to provide structural rigidity for the circuit board.

5. A structure as claimed in claim 4, wherein said two plates are madeof aluminum.

6. A structure as claimed in claim 1, wherein said bonding meanscomprises a fabric matrix impregnated with a bonding cement.

7. A structure as claimed in claim 6, wherein said two plates are madeof aluminum; said bonding cement comprising epox- 8. A structure asclaimed in claim 7, wherein said fabric matrix is a preform offiberglass.

9. The method of pneumatically interconnecting the components of apneumatic instrument, comprising the steps of:

pressure-forming a first plate of relatively soft and formable materialto develop a complex pattern of ridgelike elements defining on theopposite sides thereof grooves running laterally along the face of theplate; positioning a second plate in abutting face-to-face relationshipwith respect to said first plate to form with said grooves acorresponding series of fluid passageways;

b'onding said two plates together to effect a pressuretight seal for thepassageways and to produce a composite laminate structure; and

mounting said components on at least one of said plates in communicationwith said passageways in a predetermined interconnection pattern.

10. The method of claim 9, wherein said first plate is made of thinaluminum.

ll. The method of claim 10, including the step of cleaning the surfaceof said aluminum plate and applying theretoa conversion coating.

12. The method of claim 11, wherein said bonding is produced by a resincured at relatively high temperature.

13. The method of claim 12, wherein said bonding is produced by an epoxypreform inserted between said two plates and cured under pressure.

14. The method of making a structure for supporting and pneumaticallyinterconnecting components of an instrument for industrial processes,comprising the steps of:

pressure-forming a first planar plate of relatively soft and formablemetal with a predetermined pattern of lateral grooves;

forming a second planar plate of metal with holes in a predeterminedarrangement corresponding to said predetermined pattern of grooves topermit connection to be established thereto when the two plates areassembled;

assembling said two plates together with an intermediate sheet of resincement; and

activating said resin to bond together said two plates whereby saidgrooves become sealed passageways, for conducting pneumatic pressuresignals to or from components mounted on said second planar plate.

15. The method of claim 14, wherein said sheet of resin cement is firstblanked out in a geometrical configuration corresponding to that of saidfirst plate.

16. The method of claim 15, wherein said sheet is a fabric matriximpregnated with a resin and a catalyst.

17. The method of claim 14, wherein said two plates are made ofaluminum.

18. The method of claim 17, wherein said first plate is stretch-leveledto flatten its bonding surface.

19. The method of claim 17, including the step of piercing the firstplate with alignment holes, and thereafter flattening said first plateto assure good bonding.

20. The method of claim 17, including the step of stamping said secondplate to form a geometrical configuration corresponding to said firstplate.

21. For use with pneumatic instruments and the like, a unitary circuitboard assembly comprising a support panel, and a circuit panel mountedin lamination form -on said support panel, said circuit panel havingtherein pneumatic pas sage grooves facing internally of said assemblyagainst said support panel whereby said support panel completed saidgrooves into sealed passageways, and openings in said circuit boardassembly communicating with said passageways as means forinterconnecting instrument components without the use of conventionalinterconnecting piping or tubing, said assembly being in the form of apanel, edge mounted, top and bottom, in guide rails provided therefor inan instrument housing. I i 22. A circuit board assembly according toclaim 2l,'wherein said guide rails are provided at one side of saidinstrument housing.

23. A circuit board assembly according to claim 21, wherein saidassembly comprises an elongate support panel, with an element clearanceopening therethrough at one end thereof, and a short circuit panel,sandwiched to said support panel at the other end thereof.

24. A circuit board assembly according to claim 21, wherein saidopenings in said circuit board comprise passages through said supportpanel, with certain of said openings being located at one end of saidassembly for placement at the rear of the instrument for introducingsupply pressures to said assembly, and exiting signal pressurestherefrom, the remainder of said circuit board openings other than holesfor mounting screws and alignment rivets, comprising pneumatic passageleads to, from, and between instrument components to be mounted on saidcircuit board assembly.

25. A circuit board assembly according to claim 21, wherein said circuitpanel pneumatic passage grooves are distributed throughout said panel inappearance like a scattering of deadended worm-tunnels, except for theaccess passages provided by said openings in said circuit board assemblycommunicating with said grooves.

26 A pneumatic circuit board instrument assembly comprising a narrowrectangular housing comprising top and bottom internally grooved guiderails, sidewall members mounted in certain of the grooves of said topand bottom guide rails, a laminated circuit board assembly mounted inothers of the grooves of said guide rails, a rear wall unit providedwith pneumatic access passages to said circuit board assembly, and afront wall unit as an indicator panel for said instrument assembly.

27. An instrument assembly according to claim 8, wherein said circuitboard assembly comprises a support panel, and a circuit panel mounted inlamination form on said support panel, said circuit panel having thereinvarious pneumatic passage grooves facing internally of said assemblyagainst said support panel whereby said support panel completes saidgrooves into sealed passageways, and openings in said circuit boardassembly connecting with said passageways as a means for interconnectinginstrument components without the use of conventional interconnectingpiping or tubing.

28. The circuit board structure of claim 1, wherein said second plate issubstantially thicker than said first plate to provide structuralstrength assuring the rigidity of the circuit board.

29. The circuit board structure of claim 28, wherein both of said platesare made of aluminum.

30. The circuit board structure of claim 29, wherein the bondingmaterial is restricted to the regions between the passageways, so thatthe passageways are free of bonding material.

31. For use with fluid-operated devices such as pneumatic instrumentsand the like, a circuit board assembly for establishing fluidinterconnections between instrument components mounted and supported onthe circuit board, said assembly comprising:

a first plate of relatively thin material formed in selected regionswith a predetermined complex pattern of ridgelike elements defining onthe opposite sides thereof grooves extending laterally along the plate;

a second plate having substantially greater structural strength thansaid first plate and providing rigidity for the assembly, said secondplate abutting said first plate in face-to-face relationship andcooperating with said grooves to establish closed passageways for thetransmission of fluid under pressure;

means bonding said two plates together to produce a composite laminatedsandwich providing pressuretight sealing of said passageways; and

at least one fluid-operated instrument component mounted on said circuitboard structure;

said circuit board structure being formed to provide fluid connectionbetween said one instrument component and at least one of saidpassageways.

said plates are formed of aluminum sheets, said first plate ofrelatively thin aluminum being pressed-formed with ridgelike elements,the other plate being formed with openings to effect fluid communicationbetween said one passageway and said instrument component, saidcomponent being mounted directly on said second plate.

t F it t 1

2. A structure as claimed in claim 1, wherein said first plate isstretch-formed with said ridges and said second plate is formed withsaid openings communicating with said passageways.
 3. A structure asclaimed in claim 2, including at least one pneumatic component securedto said second plate and positioned over at least one of said openingsto establish communication therewith.
 4. A structure as claimed in claim3, wherein said first and second plates are made of metal; said secondplate being thicker than said first plate to provide structural rigidityfor the circuit board.
 5. A structure as claimed in claim 4, whereinsaid two plates are made of aluminum.
 6. A structure as claimed in claim1, wherein said bonding means comprises a fabric matrix impregnated witha bonding cement.
 7. A structure as claimed in claim 6, wherein said twoplates are made of aluminum; said bonding cement comprising epoxy.
 8. Astructure as claimed in claim 7, wherein said fabric matrix is a preformof fiberglass.
 9. The method of pneumatically interconnecting thecomponents of a pneumatic instrument, comprising the steps of:pressure-forming a first plate of relatively soft and formable materialto develop a complex pattern of ridgelike elements defining on theopposite sides thereof grooves running laterally along the face of theplate; positioning a second plate in abutting face-to-face relationshipwith respect to said first plate to form with said grooves acorresponding series of fluid passageways; bonding said two platestogether to effect a pressuretight seal for the passageways and toproduce a composite laminate structure; and mounting said components onat least one of said plates in communication with said passageways in apredetermined interconnection pattern.
 10. The method of claim 9,wherein said first plate is made of thin aluminum.
 11. The method ofclaim 10, including the step of cleaning the surface of said aluminumplate and applying thereto a conversion coating.
 12. The method of claim11, wherein said bonding is produced by a resin cured at relatively hightemperature.
 13. The method of claim 12, wherein said bonding isproduced by an epoxy preform inserted between said two plates and curedunder pressure.
 14. The method of making a structure for supporting andpneumatically interconnecting components of an instrument for industrialprocesses, comprising the steps of: pressure-forming a first planarplate of relatively soft and formable metal with a predetermined patternof lateral grooves; forming a second planar plate of metal with holes ina predetermined arrangement corresponding to said predetermined patternof grooves to permit connection to be established thereto when the twoplates are assembled; assembling said two plates together with anintermediate sheet of resin cement; and activating said resin to bondtogether said two plates whereby said grooves become sealed passagewaysfor conducting pneumatic pressure signals to or from components mountedon said second planar plate.
 15. The method of claim 14, wherein saidsheet of resin cement is first blanked out in a geometricalconfiguration correspOnding to that of said first plate.
 16. The methodof claim 15, wherein said sheet is a fabric matrix impregnated with aresin and a catalyst.
 17. The method of claim 14, wherein said twoplates are made of aluminum.
 18. The method of claim 17, wherein saidfirst plate is stretch-leveled to flatten its bonding surface.
 19. Themethod of claim 17, including the step of piercing the first plate withalignment holes, and thereafter flattening said first plate to assuregood bonding.
 20. The method of claim 17, including the step of stampingsaid second plate to form a geometrical configuration corresponding tosaid first plate.
 21. For use with pneumatic instruments and the like, aunitary circuit board assembly comprising a support panel, and a circuitpanel mounted in lamination form on said support panel, said circuitpanel having therein pneumatic passage grooves facing internally of saidassembly against said support panel whereby said support panel completessaid grooves into sealed passageways, and openings in said circuit boardassembly communicating with said passageways as means forinterconnecting instrument components without the use of conventionalinterconnecting piping or tubing, said assembly being in the form of apanel, edge mounted, top and bottom, in guide rails provided therefor inan instrument housing.
 22. A circuit board assembly according to claim21, wherein said guide rails are provided at one side of said instrumenthousing.
 23. A circuit board assembly according to claim 21, whereinsaid assembly comprises an elongate support panel, with an elementclearance opening therethrough at one end thereof, and a short circuitpanel, sandwiched to said support panel at the other end thereof.
 24. Acircuit board assembly according to claim 21, wherein said openings insaid circuit board comprise passages through said support panel, withcertain of said openings being located at one end of said assembly forplacement at the rear of the instrument for introducing supply pressuresto said assembly, and exiting signal pressures therefrom, the remainderof said circuit board openings other than holes for mounting screws andalignment rivets, comprising pneumatic passage leads to, from, andbetween instrument components to be mounted on said circuit boardassembly.
 25. A circuit board assembly according to claim 21, whereinsaid circuit panel pneumatic passage grooves are distributed throughoutsaid panel in appearance like a scattering of dead-ended worm-tunnels,except for the access passages provided by said openings in said circuitboard assembly communicating with said grooves. 26 A pneumatic circuitboard instrument assembly comprising a narrow rectangular housingcomprising top and bottom internally grooved guide rails, sidewallmembers mounted in certain of the grooves of said top and bottom guiderails, a laminated circuit board assembly mounted in others of thegrooves of said guide rails, a rear wall unit provided with pneumaticaccess passages to said circuit board assembly, and a front wall unit asan indicator panel for said instrument assembly.
 27. An instrumentassembly according to claim 8, wherein said circuit board assemblycomprises a support panel, and a circuit panel mounted in laminationform on said support panel, said circuit panel having therein variouspneumatic passage grooves facing internally of said assembly againstsaid support panel whereby said support panel completes said groovesinto sealed passageways, and openings in said circuit board assemblyconnecting with said passageways as a means for interconnectinginstrument components without the use of conventional interconnectingpiping or tubing.
 28. The circuit board structure of claim 1, whereinsaid second plate is substantially thicker than said first plate toprovide structural strength assuring the rigidity of the circuit board.29. The circuit board structure of claim 28, wherein both of said platesare made of aluminuM.
 30. The circuit board structure of claim 29,wherein the bonding material is restricted to the regions between thepassageways, so that the passageways are free of bonding material. 31.For use with fluid-operated devices such as pneumatic instruments andthe like, a circuit board assembly for establishing fluidinterconnections between instrument components mounted and supported onthe circuit board, said assembly comprising: a first plate of relativelythin material formed in selected regions with a predetermined complexpattern of ridgelike elements defining on the opposite sides thereofgrooves extending laterally along the plate; a second plate havingsubstantially greater structural strength than said first plate andproviding rigidity for the assembly, said second plate abutting saidfirst plate in face-to-face relationship and cooperating with saidgrooves to establish closed passageways for the transmission of fluidunder pressure; means bonding said two plates together to produce acomposite laminated sandwich providing pressuretight sealing of saidpassageways; and at least one fluid-operated instrument componentmounted on said circuit board structure; said circuit board structurebeing formed to provide fluid connection between said one instrumentcomponent and at least one of said passageways.
 32. The circuit boardstructure of claim 31, wherein said one component is mounted directly onsaid second plate.
 33. The circuit board assembly of claim 31, whereinsaid component includes a fluid pressure chamber having as one wallthereof a thin planar element responsive to fluid pressures, saidchamber being connected through said circuit board structure to said onepassageway.
 34. The circuit board assembly of claim 31, wherein both ofsaid plates are formed of aluminum sheets, said first plate ofrelatively thin aluminum being press-formed with ridgelike elements, theother plate being formed with openings to effect fluid communicationbetween said one passageway and said instrument component, saidcomponent being mounted directly on said second plate.